Copper-doped titania photocatalysts for simultaneous reduction of CO2 and production of H2 from aqueous sulfide

Copper-doped titanium dioxide materials with anatase phase (Cu-TiO2, atomic Cu contents ranging from 0 to 3% relative to the sum of Cu and Ti), and particle sizes of 12–15nm, were synthesised by a solvo-thermal method using ethanol as the solvent and small amounts of water to promote the hydrolysis-condensation processes. Diffuse reflectance UV–vis spectroscopy show that the edges of absorption of the titania materials are somewhat shifted to higher wavelengths due to the presence of Cu. X-ray photoelectron spectroscopy (XPS) indicate that Cu(II) is predominant. Photocatalytic CO2 reduction experiments were performed in aqueous Cu-TiO2 suspensions under UV-rich light and in the presence of different solutes. Sulfide was found to promote the efficient production of H2 from water and formic acid from CO2. The effect of the Cu content on the photoactivity of Cu-TiO2 was also studied, showing that copper plays a role on the photocatalytic reduction of CO2.